Exodus 27:20-21

Oil for the Lampstand 20“Command the Israelites to bring you clear oil of pressed olives for the light so that the lamps may be kept burning. 21In the tent of meeting, outside the curtain that shields the ark of the covenant law, Aaron and his sons are to keep the lamps burning before the LORD from evening till morning. This is to be a lasting ordinance among the Israelites for the generations to come.